1. Field of the Invention
The present invention relates to a zoom lens system. Moreover, the present invention relates to an electronic image pickup apparatus such as a digital camera.
2. Description of the Related Art
In recent years, replacing a silver-salt film camera, a digital camera in which, an object is photographed by using a solid image pickup element such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) has become a mainstream. Furthermore, there are several categories of digital cameras in a wide range, from a high-function type for professional use to a compact popular type. A user of the popular type digital camera seeks to enjoy photography readily, anywhere at any time with a wide range of scenes. In light of this, a small size camera, particularly a slim digital camera which can be accommodated easily in a pocket of clothes or a bag, and carried conveniently has been preferred.
On the other hand, while a magnification ratio of about 3 for a digital camera of a compact type has been common, a camera of a higher magnification ratio than the conventional one for widening a photography area has been sought.
As a type of a zoom lens system which is capable of achieving a high magnification (zooming) ratio, a zoom lens system having a structure of three or more lens units including in order from an object side, a first lens unit having a positive refracting power, a second lens unit having a negative refracting power, and a third lens unit having a positive refracting power has hitherto been known. For example, as a zoom lens system having approximately 4.5 times zooming ratio, zoom lens systems in Japanese Patent Application Laid-open Publication Nos. 2005-242116, 2005-326743, and 2006-78979 have hitherto been known.
In these zoom lens systems, for making it susceptible to have a magnification (zooming) function to a second lens unit and a third lens unit, at a telephoto end with respect to a wide angle end, a first lens unit and a third lens unit are moved toward an object side, and the second lens unit is either fixed or moved toward an image side.